Protective Graphite Coating for Two-Dimensional Carbon/Carbon Composites

Two-dimensional carbon/carbon(2D C/C)composites are a special class of carbon/carbon composites,generally obtained by combining resin-impregnated carbon fiber clothes,which are then cured and carbonized.This study deals with the preparation of a protective coating for these materials.This coating,based on graphite,was prepared by the slurry method.The effect of graphite and phenolic resin powders with different weight ratios was examined.The results have shown that the coating slurry can fill the pores and cracks of the composite surface,thereby densifying the surface layer of the material.With the increase of the graphite powder/phenolic resin weight ratio,the coating density is enhanced while the coating surface flatness decreases;moreover,the protective ability of coating against erosion first increases(from 1:3 to 2:2)and then decreases(from 2:2 to 3:1).When the weight ratio is about 1:1,the coating for 2D C/C composites exhibits the best erosion resistance,which greatly aids these materials during gas quenching.In this case,the erosion rate is decreased by approximately 41.5%at the impact angle of 30°and 52.3%at normal impact,respectively.This can be attributed to the ability of the coating slurry to infiltrate into the substrate,thereby bonding the fibers together and increasing the compactness of the 2D C/C composites.

Effects of Conductive Carbon Black on Thermal and Electrical Properties of Barium Titanate/Polyvinylidene Fluoride Composites for Road Application

In the field of roads,due to the effect of vehicle loads,piezoelectric materials under the road surface can convert mechanical vibration into electrical energy,which can be further used in road facilities such as traffic signals and street lamps.The barium titanate/polyvinylidene fluoride(BaTiO_(3)/PVDF)composite,the most common hybrid ceramic-polymer system,was widely used in various fields because the composite combines the good dielectric property of ceramic materials with the good flexibility of PVDF material.Previous studies have found that conductive particles can further improve the dielectric and piezoelectric properties of other composites.However,few studies have investigated the effect of conductive carbon black on the dielectric and piezoelectric properties of BaTiO_(3)/PVDF composites.In this study,BaTiO_(3)/PVDF/conductive carbon black composites were prepared with various conductive carbon black contents based on the optimum ratio of BaTiO_(3)to PVDF.The effects of conductive carbon black content on the morphologies,thermal performance,conductivities,dielectric properties,and piezoelectric properties of the BaTiO_(3)/PVDF/conductive carbon black composites were then investigated.The addition of conductive carbon black greatly enhances the conductivities,dielectric properties,and piezoelectric properties of the BaTiO_(3)/PVDF/conductive carbon black composites,especially when the carbon black content is 0.8%by weight of PVDF.Additionally,the conductive carbon black does not have an obvious effect on the morphologies and thermal stabilities of BaTiO_(3)/PVDF/conductive carbon black composites.

Enhanced Thermal Conductivity and Bending Strength of Graphite Flakes/aluminum Composites Via Graphite Surface Modification

The effect of graphite surface modification on the thermal conductivity(TC) and bending strength of graphite flakes/Al composites(Gf/Al) prepared by gas pressure infiltration were investigated. Al3 Ni and Al4C3 phase may form at the interface in Ni-coated Gf/Al and uncoated Gf/Al composites, respectively, while the Al-Cu compound cannot be observed in Cu-coated Gf/Al composites. The Cu and Ni coatings enhance TC and the bending strength of the composites in the meantime. TC of Cu-coated Gf/Al composites reach 515 Wm^-1·K^-1 with 75 vol% Gf, which are higher than that of Ni-coated Gf/Al. Meanwhile, due to Al3 Ni at the interface, the bending strength of Ni-coated Gf/Al composites are far more than those of the uncoated and Cu-coated Gf/Al with the same content of Gf. The results indicate that metal-coated Gf can effectively improve the interfacial bonding between Gf and Al.

A Novel Method for Preparing Polyurethane Based Conductive Composites with Low Percolation Threshold

A novel method for preparing conductive carbon black fllled polymer composites with low percolation threshold from polyurethane emulsion are reported in this paper. The experimental results indicate that with a rise in carbon black concentration the insulator-conductor transition in the emulsion blended composites occurs at 0.8-1.4vol%. In contrast, the solution blended composites exhibit drastic increase in conductivity at conducting filler fraction as high as 12.3-13.3vol%. It is demonstrated that the composites microstructure rather than chemical structure of the matrix polymer predominantly determines the electrical conduction performance of the composites.

Anti-oxidation behavior of chemical vapor reaction SiC coatings on different carbon materials at high temperatures

To protect carbon materials from oxidation,SiC coatings were prepared on carbon/carbon(C/C)composites and graphite by chemical vapor reaction.SEM and XRD analyses show that the coatings obtained are composed of SiC grains and micro-crystals. The influence of different carbon substrates on oxidation behavior of coated samples was investigated,and then their oxidation mechanisms were studied.Oxidation test shows that the SiC coated graphite has a better oxidation resistance than SiC coated C/C composites at high temperatures(1 623 K and 1 823 K).In the oxidation process,the oxidation curves of SiC coated C/C composites are linear,while those of SiC coated graphite follow a quasi-parabolic manner.The oxidation mechanism of the former is controlled by chemical reaction while the latter is controlled by oxygen diffusion based on the experimental results.The variation of oxidation behavior and mechanism of SiC coatings on two kinds of carbon substrates are primarily contributed to their structure differences.

Optimization of mixing speed and time to disperse the composite conductive agent composed of carbon black and graphene in lithium-ion battery slurry

This paper proposed an optimal approach to disperse the composite conductive agent which is composed of carbon black(CB)and graphene(Gr)within lithium-ion battery(LIB)slurry with different mixing speeds and mixing times.The internal structures of LIB slurry are characterized by Electrochemical Impedance Spectroscopy,Scanning Electron Microscopy,and Raman experiment.Initially,a composite conductive solution is prepared by mixing the composite conductive agent with NMP solvent under the conditions of five different mixing speeds n_(1)(n_(1)=1000,1100,1200,1300,1400 rpm)in the case of mixing time t_(1)=10 min.Subsequently,LIB slurry is prepared by blending the composite conductive solution,LiCoO_(2)and PVDF-NMP solution under the conditions of five different mixing speeds n_(2)(n_(2)=1000±280,1100±280,1200±280,1300±280,1400±280 rpm)in the case of mixing time t_(2)=6 min.By analyzing the internal structure of different LIB slurries,it shows that in the case of n_(1)=n_(2)=1200 rpm,a conductive network structure is well formed within LIB slurry.Additionally,in order to determine the optimal time to prepare the composite conductive solution for LIB slurry,nine different t_(1)(t_(1)=0,10,20,30,40,50,60,70,80 min)are selected.By analyzing the internal structure of different LIB slurries,a well-formed conductive network structure and a uniformly distributed composite conductive agent are deduced in LIB slurry when t_(1)=50 min.Therefore,it can be concluded that the composite conductive agent composed of CB and Gr is able to be uniformly dispersed in LIB slurry by establishing a well-formed conductive network structure under the optimal mixing speed n_(1)=n_(2)=1200 rpm and the optimal mixing time t_(1)=50 min,t_(2)=6 min.This kind of the internal structure has the potential to be used to further analyze the dispersion characterizations of LIB slurry under different composite conductive agent and CB/Gr ratios with the aim of improving the final performance of LIB.

Fabrication and Thermal Conductivity Improvement of Novel Composite Adsorbents adding with Nanoparticles

Thermal conductivity is one of key parameters of adsorbents, which will affect the overall system performance of adsorption chiller. To improve adsorbent＇s thermal conductivity is always one of research focuses in chemisorption field. A new chemical composite adsorbent is fabricated by adding carbon coated metal（Aluminum and Nickel） nanoparticles with three different addition amounts into the mixture of chloride salts and natural expanded graphite aiming to improve the thermal conductivity. The preparation processes and its thermal conductivity of this novel composite adsorbent are reported and summarized. Experimental results indicate that the nanoparticles are homogenously dispersed in the composite adsorbent by applying the reported preparation processes. The thermal conductivity of the composite adsorbent can averagely enlarge by 20% when the weight ratio of the added nanoparticles is 10 wt%. Moreover, carbon coated aluminum nanoparticles exhibit more effective enlargement in thermal conductivity than nickel nanoparticles. As for the composite adsorbent of CaCl2-NEG, there is a big reinforcement from 30% to 50% for Al@C nanoparticles, however only 10% in maximum caused by Ni@C nanoparticles. The proposed research provides a methodology to design and prepare thermal conductive chemical composite adsorbent.

Ir Protective Coatings for Carbon Structural Materials

Ir coatings were deposited on the heat-treated C/C composites and graphite by double glow plasma. Microstructure and morphology of the coating and substrate were observed by SEM and TEM. The effect of the surface treatment for the carbon structural materials on the microstructure of the coating was investigated. Many large gaps and pores appeared on the surface of the substrates after heat treatment. The Ir coating did not fully covered on the surface of heat-treated C/C composite and graphite substrates because of the large gaps and pores on the surface of substrates. The Ir coating exhibited excellent ablation resistance at super-high temperature. After super-high temperature ablation, the coating kept the integrity, but the coating was weekly bonded to the substrates. Some microcracks and micropores appeared on the surface of as-ablated coating. The Ir coating would need thick enough to cover and fill the large microgaps and micropores on the surface of the heat-treated C/C and graphite substrates.

In Vitro Biocompatibility of MC3T3-E1 Osteoblast-like Cells on Arg-Gly-Asp Acid Peptides Immobilized Graphite-like Carbon Coating on Carbon/Carbon Composites

Carbon/carbon （C/C） composites were deposited with graphite-like carbon （GLC） coating, and then, Arg-Gly- Asp acid （RGD） peptides were successfully immobilized onto the functionalized GLC coating. GLC coating was utilized to prevent carbon particles releasing and create a uniform surface condition for C/C composites. RGD peptides were utilized to improve biocompatibility of GLC coating. Surface chemical characterizations of functionalized GLC coating were detected by contact angle measurement, X-ray photoelectron spectroscopy and Raman spectra. Optical morphology of GLC coatings was observed by confocal laser scanning microscopy. In vitro biological performance was determined using samples seeded with MC3T3-E1 osteoblast-like cells and cultured for 1 week. Surface characterizations and morphological analysis indicated that C/C composites were covered by a dense and uniform GLC coating. Contact angle of GLC coating was reduced to 27.2° when it was functionalized by H202 oxidation at 40 ℃ for 1 h. In vitro cytological test showed that the RGD peptides immobilized GLC coating had a significant improvement in biocompatibility. It was suggested that RGD peptides provided GLC coating with a bioactive surface to improve cell adhesion and proliferation on C/C composites.

Low Temperature Preparation of Carbide Coated Carbon for Refractory Castable Applications

Titanium carbide （ TiC ） coated graphite flakes （GF） and carbon black （CB） powders were prepared at relatively low temperatures （ 750 - 950 ℃ ） using a no- vel molten salt synthesis technique. The in-situ formed TiC coatings were homogeneous and crack-free and their thicknesses could be readily controlled/tailored by simply adjusting the Ti/C ratio. Compared to their uncoated counterparts, as prepared TiC coated GF and CB showed much improved water-wettability/dispersivity and rheological properties, and thus could be potentially used to prepare carbon-containing refractory castables.

Textile-Based Sensors for Inspection of Composite Materials

The monitoring of mechanical deformation and damage of composite materials is normally performed by established analytical methods,such as strain gauges and optical and piezoelectric sensors.However,large areas outside of the measuring cell remain unconsidered.A large-area sensitive sensor for composites is presented,which is simply generated by printing a carbon layer on the reinforcing glass fiber fabrics or on any composite itself.Such printed sensors enable to determine mechanical deformations and damages of the entire component and it responds with a measurable electrical resistance to external tension or pressure without any hysteresis.The strongest influence on sensor signal was identified with low carbon concentration and thin layers.The sensors signal linearly correlates with the degree of deformation and bending velocity whereas bending direction can be identified through signal change under residual tensile stress or compressive stress.

Performance of activated carbon coated graphite bipolar electrodes on capacitive deionization method for salinity reduction

This research investigates a capacitive deionization method for salinity reduction in a batch reactor as a new approach for desalination.Reductions of cost and energy compared with conventional desalination methods are the significant advantages of this approach.In this research,experiments were performed with a pair of graphite bipolar electrodes that were coated with a one-gram activated carbon solution.After completing preliminary tests,the impacts of four parameters on electrical conductivity reduction,including(1)the initial concentration of feed solution,(2)the duration of the tests,(3)the applied voltage,and(4)the pH of the solution,were examined.The results show that the maximum efficiency of electrical conductivity reduction in this laboratory-scale reactor is about 55%.Furthermore,the effects of the initial concentration of feed solution are more significant than the other parameters.Thus,using the capacitive deionization method for water desalination with low and moderate salt concentrations(i.e.,brackish water)is proposed as an affordable method.Compared with conventional desalination methods,capacitive deionization is not only more efficient but also potentially more environmentally friendly.

CNT/乙炔黑复合导电剂对LiNi_(0.5)Co_(0.2)Mn_(0.3)O_(2)的影响

为解决乙炔黑单一导电剂自身团聚的问题,采用含碳纳米管(CNT)的导电浆料进行改性。复合后,直径80~100 nm的球形乙炔黑颗粒均匀分散在直径20 nm的CNT表面,比表面积提高至107.96 m^(2)/g。与乙炔黑导电剂电池相比,CNT/乙炔黑电池的电化学阻抗更小、CV曲线面积更大,氧化峰和还原峰的电位差较小(0.19 V),以200 mA/g在2.75~4.20 V循环,首次充放电比容量分别为151.8 mAh/g和155.5 mAh/g,首次库仑效率为97.6%。第200次循环的放电比容量为141.9 mAh/g,容量保持率为92.4%。在5.0 C倍率下,CNT/乙炔黑电池的放电比容量为116.9 mAh/g,倍率性能更好。

氧硫双掺杂CNTs水系导电剂辅助构筑高性能石墨/SiO负极

由于石墨具有资源丰富、比容量高和嵌锂电位低等优势,被视为重要的商业化锂离子电池(LIBs)负极材料。然而,石墨较低的理论比容量限制了LIBs能量密度的进一步提升。因此,本文将少量的氧化亚硅(SiO)添加到石墨中,再分散到少量的氧硫掺杂双壁碳纳米管(O,S-DCNTs)水系导电剂中,得到石墨/SiO复合负极。其中,O,S-DCNTs是通过将双壁碳纳米管(DCNTs)在空气中预氧化处理,再通过浸渍法与MgSO4混合后煅烧所得的,具有纳米孔结构丰富、硫含量高和亲水性强等特性。通过电池性能测试发现,引入O,S-DCNTs后石墨/SiO复合负极的比容量、倍率和循环性能得到显著提升。此外,其循环性能是纯硫掺杂碳纳米管(S-DCNTs)石墨/SiO负极的4倍,这主要归因于高分散的O,S-DCNTs能够构筑大量的导电网络,提供丰富的锂离子存储空间和活性位点,解决SiO导电性差和体积膨胀系数大问题,从而显著提高石墨负极的电化学性能。本文为高性能负极材料的制备与储能应用提供了新的思路和方向。

不同乙炔炭黑对涂炭铝箔性能的影响

采用三种不同的乙炔炭黑为原材料,通过扫描电子显微镜(SEM)、比表面积(BET)、激光粒度仪等对乙炔炭黑进行表征与分析。测试加入不同乙炔炭黑的浆料的稳定性和粘度变化,通过凹版涂布工序制得涂炭铝箔并进行电性能测试分析,评估三种乙炔炭黑对涂炭铝箔性能的影响。结果表明:实验室所用的乙炔炭黑颗粒团聚粒度分布在8μm左右,比表面积约为60 m^(2)/g,SP-009和Li-2060表面粗糙,具有蓬松的孔状结构,有利于活性物质嵌入,增大活性物质与箔材的接触面积。配制成浆料后,SP-009在三者中沉降最少,分散性和稳定性较好。SP-009的涂炭铝箔电阻率最小且较为集中,均值为1.95 mΩ,电阻越小,性能最优。将三者制成的电池循环性能进行对比,SP-009的电池经过循环100次后容量保持率最高,为84.46%。SP-009乙炔炭黑性能较好,提高了浆料的稳定性和涂炭铝箔的导电性能。

新型导电水泥基复合材料导电性能研究

采用炭黑作为主要导电掺料,加入少量碳纳米管和钢纤维构建高效导电网络以提高导电性能,研究其在不同环境中的稳定性以及微观形态下复相导电掺料的协同作用。结果表明:掺5%炭黑、0.3%碳纳米管、0.6%体积掺量钢纤维的导电水泥基复合材料C5P3F6固化28 d电阻率为304Ω·cm,比传统水泥基复合材料降低94.5%;掺5%炭黑、0.9%碳纳米管、0.6%体积掺量钢纤维的导电水泥基复合材料C5P9F6受水泥水化、干燥环境和温度的影响较小,表现出较为优异的稳定性。微观形态下能观察到导电掺料分散性较好,碳纳米管、钢纤维有效地与分散的炭黑协同作用桥接成为导电网络。

PP/SEBS基导电复合材料的研制

以聚丙烯(PP)和(苯乙烯/乙烯/丁烯/苯乙烯)共聚物(SEBS)的共混物为基体材料,通过掺杂炭黑和碳纤 维,用开炼法制备了一种高电导率的导电复合材料,其体积电阻率小于0.1Ω·cm,并作为集流体材料应用于全钒氧 化还原液流电池。

导电炭黑填充PP-EAA复合材料的形态及电性能

以聚丙烯（PP）和乙烯-丙烯酸共聚物（EAA）的共混物为基体材料，以导电炭黑为填料，通过熔融共混的方法制备了导电复合材料。探讨了导电炭黑在两相基体中的分散情况以及聚丙烯结晶度对复合体系导电性能的影响。扫描电镜测试结果表明，在共混物中炭黑粒子选择性分散在极性EAA树脂中，同时EAA树脂在聚丙烯基体中形成连续网络结构，从而显著降低了复合体系的渗滤阈值。电性能测试结果表明，材料在相同导电炭黑含量下的体积电阻率相对于单基体体系有7～8个数量级的降低，并且结晶度较高的PP更有利于降低复合体系的体积电阻率。此外，炭黑／PP—EAA复合材料的拉伸强度相对于炭黑／PP体系有所下降，而断裂伸长率有所提高。